Impacts of the spatial heterogeneity of atmospheric CO2 concentration on carbon-climate feedbacks

Intercomparison initiatives focusing on climate-carbon cycle models, like C4MIP, have played an important role in advancing our comprehension of the interactions between the carbon cycle and climate dynamics, shedding light on their implications for future climatic shifts. Through the application of fully integrated carbon-climate simulations, which utilize prognostic CO2 tracers in a three-dimensional framework to simulate exchanges with terrestrial and marine environments and their effect on atmospheric radiation, we gain insights into climate change mechanisms. In contrast, simulations partially coupled with the carbon cycle rely on predetermined CO2 concentration timelines to assess climate responses, lacking the ability to consider spatial variability in CO2 concentrations or the dynamic feedback loops between carbon and climate. This study leverages a land-atmosphere interactive version of the Energy Exascale Earth System Model (E3SM) v2.1, employing predefined oceanic CO2 fluxes to scrutinize the impact of atmospheric CO2's geographic variability on land-atmosphere coupling. By adopting prescribed oceanic fluxes, computational demands are mitigated, facilitating the exploration of interactions between terrestrial biogeochemistry (BGC) and atmospheric processes. This approach involves conducting paired simulations, with and without the incorporation of three-dimensional atmospheric CO2 concentrations, to evaluate their influence.